二叉树层次遍历

void printByLevel(Tree t)
{
    Tree p;
    queue<Tree> q;
    q.push(t);
    while (!q.empty())
    {
        p = q.front();
        q.pop();
        cout << p->val << " ";
        if (p->left)
            q.push(p->left);
        if (p->right)
            q.push(p->right);
    }
}